Sensitive photographic materials



Patented Mar. 7, 1950 UNITED STATES ATENT OFFICE England, assignors to Eastman Kodak Gompany, Rochester, N. Y., a, corporation of New Jersey No Drawing. Application March 6, 1947, Serial No. 732,934. In Great Britain April 1, 1946 (Jlairns.

l Ihis invention relates to sensitive photographic materials, and to sensitive silver halide developing-out emulsions, as contrasted with printingout emulsions.

Developing-out emulsions can to-day be broad- 5 the following reducing. agents, arsenites, Stall-1 l-y divided into two classes, namely (1) those nites, phosphites, metaphosphites, hypophoswhich give a strong negative image from more phites, antimonites, hyposulphites and germadevelopment, that is to say, upon development nites. Alkali or ammonium salts are especially the silver salt darkens most in those places, where advantageous. These compounds reduce an amthe most light fell during the imagewise expol0 moniacal solution of silver nitrate to silver, at sure, and (2) those which give a strong positive least when the solutionis warmed. image upon mere development, that is to say, The emulsion may comprise silver bromo-iodide. upon development the silver salt darkens most which is formed by adding a soluticnof: silver in those places where the least light fell during nitrate to a solution of. a soluble bromide and the image-wise exposure. a soluble iodide, in which case, the said reduc The present invention is directed to the manuing agent may be incorporated'in the last menfacture of emulsions of the latter class, which tioned solution. are known as direct positive emulsions. Such Emulsions which have been ripened by treatemulsions may be coated on films, plates, papers ment with ammonia are preferred; although nonor tracing cloth or the like. ammoniaoal emulsions will give a fair result. We.

Emulsions of both classes (1) and (2) are preferably employ silver bromo-iodide emulsions made with similar ingredients which are usually containing up to 20% of silver iodide based on compounded by much the same technique, except the total weight of silver bromide and iodide, but that for class (2) the emulsion is given an addiemulsions in which the only silver halide is silver tional treatment. The reason for this is that bromide can be used. Digestion of the emulsion nearly all developing-out emulsions of class (1) (i. e. after washing) may be desirable in some will tend to give a positive upon development if cases. However, the emulsion may; be coated the image-wise exposure is long enough. The if desired immediately after the ripening treat-. phenomenon has been known for a very long ment (i. e. without washing). time and is called solarisation. The emulsions In the examples below, the quantities in which are specially treated so as to. fall into brackets give arough ideaof the amount usually class (2), give a very much better positive and found to give useful results in an amount of, with little image-wise exposure. emulsion containing 100 grams of Ag.

Various methods of making direct positive Phosphites (e. g. metaphosphites and hypoemulsions are known, for instance, y merely phosphites) give good speeds and very clean pre-fogging an emulsion of class (1). Another whites, for example. m i Is to cause chemtcal fPggmg dumtg Sodium metaphosphitesNaPoz (2.36 grams) ripening. Another method 1s to incorporate in s 1 odium phosphites, Na2I-IPO3.5H2O (0.8 gram) a finished emulsion about 1A to 4 times the Sodium h o hos hits NaH PO H O (1.6 amount of a non-acid optical sensitizing dye re- 40 yp p p 2 2 quired to give optimum sensitizing together with grams a photographic developing agent. Arsenites give good speeds and very clean The problem to which most of the prior sugwhites, fOr example, commercial sodium arsenite gestions have been directed is to make a direct (Probably Sodiumv metarsenite), NaASOZ positive emulsion which requires relatively little r image-wise exposure and upon development gives Antimonites give good speeds and very clean. an image which is of good contrast with deep es, r e p e, sodium antimonite, NaSbOz blacks and clean whites, but all known methods (1.6 a s)- still leave much to be desired in these directions. Stannites give good results but have some ten- The present invention enables improved results 5 dency to cause staining, for example, sodium of this kind to be obtained. stannite, NaHsnOz. (0.008 gram).

In the present invention We employ reducing Hyposulphites give very good results with clean agents containing elements selected from groups whites in some cases, for example, sodium hypo- IV, V and VI of the periodic table. s-ulphite, NazS2O4.2H2 O. (0.016 gram). Sulphites The present invention is based on the discovery 55, have insuflicient, reducing power.

of the emulsion there is present during the forma-.

tion of the sensitive silver. salt one or more of.

The above-mentioned antimonite was prepared specially by dissolving antimonous oxide in caustic soda. The stannite was prepared by adding caustic soda to stannous chloride solution (SnClz), until the precipitate first formed was redissolved and using the solution so obtained.

If desired, the emulsion so made may also be chemically fogged or light fogged. Almost any known chemical fogging agent can be used but some cause dirty whites: the chemical fogging agent is preferably added before the end of the ripening step. Good results have been obtained using hydrazine formaldehyde, hydroxylamine or excess of silver nitrate. Mere extra digestion of the emulsion or extra digestion with sulphur sensitizers such as sodium thiosulphate can be used for this purpose.

We prefer to employ for the emulsion an ammoniacal type, for example:

Solution A Potassium bromide "grams" 132 Potassium iodide do 115 Gelatin do 60 Reducing agent .1 Water cc 2,500

The reducing agent may be any one of the following, the quantity at being as indicated.

Sodium arsenite grams 3.5 Sodium phosphite do 1.0 Sodium hyposulphite d 0.2 Sodium stannite do 0.007

Solution B Silver nitrate grams 195 Water to cc 400 To solution B at room temperature add slowly with stirring in the usual way, sufiicient ammonia solution (0.880 sp. gr.) until the precipitate first formed is just redissolved and raise the temperature of the mixture to 65 C. Now add solution B to solution A at 65 C. taking a few minutes to efiect this. Ripen the emulsion for 30 minutes at 65 C. Then add 200 grams of gelatin. Then ripen a further 15 minutes at 65 C. Then allow the emulsion to cool and set and wash in the: usual manner, until the emulsion has a pH of 7.2. Melt the emulsion and add 50 cos. of 20% solution. of potassium bromide and make up to 3 litres with water. The autopositive emulsion so made may now be coated and will give a positive image providing the exposure is suiilcient. If it is found that the maximum density obtained in such positive image is insuficient, then instead of coating after washing, digest the emulsion for about hour at 65 C. and then coat. Emulsions so made will give negative images on low exposures: the production of such negative images can be avoided by fogging the emulsion, for instance, the emulsion can be fogged chemically by adding say 005 to 0.2 gram of hydrazine hydrochloride or 3.0 cos. of 20% formaldehyde to the emulsion immediately after solution B has been added to solution A.

The emulsions made according to the present invention, may be sensitized with sensitizing dyes especially mere-cyanines and cyanines and in. this case the amount of dye may be advantageously greater than the optimum quantity of dye relative to the usual amounts used for sensitizing purposes, as described in United States Patent No. 2,184,013, it being not essential to add a developing agent as therein given.

If desired a developing agent such as hydroquinone can be incorporated in the emulsion so 4 that after exposure of the emulsion it can be developed merely by immersion in an alkaline solution. By using an unhardened emulsion, alkaline hydroquinone development or other tanning developer will tan the emulsion imagewise, in which case the untanned portions can be washed off immediately after development or at a later stage.

A typical developer which may be used for developing emulsions made according to the present invention is as follows:

Elon grams 2.2 Sodium sulphite (cryst.) do 144 (or anhydrous) do ('72) Hydroquinone do 8.8 Sodium carbonate (cryst.) do 130 (or anhydrous) do (48) Potassium bromide do 4 (or 10% solution) cc (40) Water to make cc 1000 What we claim as our invention and desire to be secured by Letters Patent of the United States is:

1. The method of making a direct positive developing out silver salt emulsion which comprises forming the sensitive silver salt in the presence of an amount of a reducing agent of the class consisting of about 3.1 grams of an arsenite, about 0.008 gram of a sta-nnite, from 0.8 to 2.36 grams of a phosphite, about 1.6 grams of an antimonite and about 0.016 gram of a hyposulphite, each per grams of silver in the emulsion.

2. The method of making a direct positive developing out emulsion according to claim 1 wherein the emulsion is of the ammoniacal type. 3. The method of making a direct positive developing out silver salt emulsion according to claim 1 wherein the emulsion is fogged during manufacture.

4. A direct positive silver halide emulsion containing an amount of reducing agent of the class consisting of about 3.1 grams of an arsenite;

about 0.008 gram of a stannite, from 0.8 to 2.36 grams of a phosphite, about 1.6 grams of an antimonite and about 0.016 gram of a hyposulphite, each per 100 grams of silver in the emulsion, said silver halide having been formed in said emulsion in the presence of at least one of said reducing agents.

5. A silver halide emulsion according to claim 4-. and containing a developing agent.

ERIC F. TEAL. EDWARD P. DAVEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,005,837 Arens June 25, 1935 FOREIGN PATENTS Number Country Date 462,730 Great Britain Mar. 15, 1937 OTHER REFERENCES British Journal of Photography, vol. 70, November 23, 1923, pages 717-720. (Copy in Scientific Library.)

The Photographic Journal, Great Britain, August 1924, pages 363-369. (Copy in Scientific Library.) 

1. THE METHOD OF MAKING A DIRECT POSITIVE DEVELOPING OUT SILVER SALT EMULSION WHICH COMPRISES FORMING THE SENSITIVE SILVER SALT IN THE PRESENCE OF AN AMOUNT OF A REDUCING AGENT OF THE CLASS CONSISTING OF ABOUT 3.1 GRAMS OF AN ARSENITE, ABOUT 0.008 GRAM OF A STANNITE, FROM 0.8 TO 2.36 GRAMS OF A PHOSPHITE, ABOUT 1.6 GRAMS OF AN ANTIMONITE AND ABOUT 0.016 GRAM OF A HYPOSULPHITE, EACH PER 100 GRAMS OF SILVER IN THE EMULSION. 